Manufacturing process for electrolytic nickel



United States Patent Ofiice 3,028,223 Patented Apr. 3, H62

3,02 ,223 MANUFACTURING PIRGCESS FOR ELECTRO- LYTIC.N.II(IKEL J Taro Horii, 126 Kairiifujimaecho, 'Komagome, Bunkyo- *ku, and Keiichi "Maejin'aa,"6' 10 3-'chome, Azusawamachi,ltabashi-kuibothof Tokyo, Japan" 4 No-Drawing. FiledO'ct. 6, 1 95s, ser. No. 765,313 "Claims priority,'-'.applicationJapan Oct. *12, 1957 8*Clairns; (Cl. 23-2'2'4) This invention relates to a manufacturing process for electrolytic nickel r a 1 An object of this invention resides in the provision of a process or method for obtaining substantially pure nickel in a convenient and inexpensive manner A further object of this'invention resides in the provision of a process of producing electrolytic nickel without requiring-excessive amounts ofelectric'po wer or expensive anode or cathode materials or catalysts.

Manufacturing process for electrolytic nickel may be roughly divided into two classes, i.e. a non-soluble anode process and a soluble anode process.

In the non-soluble anode process, lead or carbon is used as an anode and therefore carbon or lead will form impurities which will be mixed in the final products. Additionally, because of considerable amount of gas contained in the final product of a non-soluble process, a desirable final product can not be obtained. Consequently, only the soluble anode process is presently practical for use in industry. 1 The soluble-anode 'process may be further subdivided into two processes, i.e.; one in which nickel matte is used as an anode and anotherprocess-in--which-the -nickel matte has its sulphur content removed and then it is reduced and 'smelted"to make so called crudemiokel anode These two' soluble anode processes have certain advantages and disadvantages as follows:

Because of its high content of sulphur, a nickel matte anode is relatively passive and the requiredelectrolytic voltage becomes higher and the corrosive etficiency of anode becomes lower than that of cathode," so thatthe acidity of waste liquid becomes higher (pH is lowered) and-in subsequehtstage of deferri'zation 'refining,-'a large amount of nickel carbonate (neutralizing agent) is wasted. However, a nickel matte anode"can be used more simply and far more economically than acrude nickel anode.

A crude nickel anode will scarcely become passive, i.e., both nickel efiiciency of anode and cathode'are almost eqi1al,"a'nd therefore "there is'very' 'little pfoduetiori or acid and theprocess requires only asmall amount of neutralizing agent; "While additional sta es such as do sulphurization and subsequent-reducing;etcs; are-required,

which result in greater'lossof material and expense, and since during such stages more complicated apparatus than apparatus required for use with a nickel matte anode is required, it is far more expensive to employ a crude ,nickel anode.

Eachof the above processes has advantages and disadvantages respectively, and it is therefore an important object of the present invention to provide a process com bining" the best'feat-ures of 'both processes-"of" employing nickelmatte and crude nickel.

The new process is carried out by making the current density of cathode especially large in a neutralizing electrolytic step wherein free acid of nickel electrolytic waste liquid using said matte anode is neutralized and at the same time, nickel hydroxide is by-produced which is well adapted for reducing nickel raw material. Then the current density of cathode is made smaller to some degreefor the neutralization of waste liquid andtpr ob taining at the safme-timepowder nickelasby-p'rd'dric't h the cathode, the latter being used for removing copper content in the waste liquid as the reducing nickel'powder. Thus the electrolytic nickel is obtained in'an advantageous manner and at the'same time, nickel carbonate is not required in the deferrization stage and therefore unrefinable alkaline earth metal is not accumulated in the electrolyte, so that an excellent final product is always obtained.

The concept of this invention primarily consists in the combination of three steps, i.e.,-an electrolytic step, an electrolytic neutralizingstep, and then 'a liquid refining step. It is to be noted that the refined liquid obtained from the liquid refining step is circulated in the electrolytic step as follows.

The first or electrolytic step: This is a manufacturing step for producing high purity electrolytic nickel, wherein an anode is made of nickel matte and the cathode is placed within a cathode box to which a refined liquid commensurate that obtained in the third step is in troduced. Anode slime by-produced in this first step is primarily sulphur containinga small amount of nickel matte, so that it may be mixed with a sulphur fixin a em including lime, etc., and repeatedly used in'a smelting-mama to recover nickel matte and sulphur in the slime for use, or by heating, gasifying and cooling in the absence of air, to recover high purity sulphur and at the sai rie time to recover nickel matte'from the furnace bottom. The second or electrolytic neutralizing 'step'i: Since the anodewaste liq'uid'of the'precedingstep is mixed with copper and iron as impurities and besides, free acid is increased in proportion 'to' quiescent or passive part of the matte anode (usuallythe passive proportion is'about 10-15%) and pH of the'liquid'is lowered,the acid is neutralized only by electrolytic process without rising any nickel carbonate. e

To depositelectrochemically the nickel from aqueous solutionth ereof, following conditions are considered; Now, let E be equilibrium potential at nickel andE be equilibrium potential of'hydrogen, (1') WhenE 'E i, nickel is deposited and hydrogen is notgenerated," i (2 When'F =E nickel is deposited and hydrogen is generated' as' well, I (3) When"E E only 'riickel is not deposited.

If E is replaced with CD. (current density), same results will be obtained and in this invention, the neutralizing electrolysis is performed, under the conditions of'Zand 3 i I In this process, above mentioned Waste liquid is used as electrolyteand nickel matte' or crude nickel or pure nickel, depolarized nickeljc'ar bonized nickel, etc, are used'as anode material, while'pl'atef'rod and wire made of metals such as'nickel, copper and iron, etc, or of alloys based on Ni, Cu and Fe, etc., are used as cathode material. The surface area of the cathode is made far smaller than that of anode, thus the electrolysis is' performed. Then, (a) at the anode side, i

and the nickel is corroded and the acid is neutralized, (b) at the cathode sidej'as the current density is very high (becausethe'surfa cearea issma'll), only a'very small am'ou'htof nickel is depositedbut an electrolytic reactionof'water takes place according to' the formula H O=H++OH the'hydrogen being violently generated and the OH ion remains 'andreactswith thenickel the electrolytic Iiquid,"suspendiiig' ba'sic nickel Bye-shaman eifectingthe neutralizing reaction". i

Thereupon, in case ofnecessity, if a part ofcathode is inserted with a largersurface area, powdered: reducing nickel is easily obtainedas by prh duct. Thus, hfefneu hydrogen is generated and tralizing electrolysis of the second step is performed at both anode and cathode sides simultaneously, so that such neutralizing agents as nickel carbonate or calcium carbonate, etc., as used in the prior art are entirely unnecessary and the neutralizing is promptly effected with electrolysis only. Namely, this neutralizing electrolysis is performed by lowering exceedingly the nickel efiiciency of cathode with respect to the nickel efficiency of the anode, and it is performed without any trouble even when there is any inactivity as the case of nickel matte, so that any suitable material such as nickel matte, crude nickel, depolarized anode and carbonized anode may be used therefor. This step may be also adapted successfully for removing iron content accumulated in a nickel plating bath.

The third or liquid refining step: When the neutralized liquid is shifted to a deferrization tank and oxidized by air or other oxidizing agent, the iron is precipitated as ferric hydroxide, and is then filtrated and after the copper content has been replaced by adding reducing nickel powder to the neutralized liquid, it is filtrated and pH thereof is adjusted. Then the liquid can be used in the first step.

In this third step, it matters little whether the deferrization is completed before the decuprization (copper removing) as above mentioned or conversely, the decuprization is before the deferrization.

According to the process of the present invention, the increase of acidity (which is a defect of the matte anode process) is entirely corrected by the neutralizing electrolysis of the second step, and in case of necessity, powdered reducing nickel is obtained as a by-product. No additional neutralizing agent is required upon neutralization, so that any impurity of alkaline earth metals incapable of liquid refining is not added to the liquid, which is a remarkable advantage for maintaining constant composition of the electrolyte. From the commercial viewpoint, the manufacturing cost is considerably lowered, because an additional neutralizing agent is unnecessary and yet perfect emulsifying is effected.

The productive capacity of electrolytic tank in this neutralizing electrolysis is suflieient to produce the amount of liquid needed for the nickel matte electrolysis of the first step. Therefore, the invention is far more easily and cheaply practiced compared with the crude nickel anode process of prior art, and with better effect.

The process of the present invention will be explained in detail referring to the following examples.

Example I The first step: A nickel matte anode is put in a one-litre beaker and a cathode is made by putting nickel plate in a cathode box of canvas, into which the liquid obtained from the third step is poured by dropping and the electrolysis is performed under the following conditions. (a) The composition of liquid obtained from the third step:

Ni 40.6 g./l., H B 28.7 g./l.

C1 radical 25.3 g./l., pH 4.0 (b) Electro-deposition nickel:

Ni-l-Co 99.95%, Cu 0.0037%, Fe 0.0045 (c) Conditions of electrolysis:

El. voltage 2.8 v., e1. current 0.6 A.,

Current density 130 a./m. temperature 55 C. (d) Composition of anode waste liquid at this time:

pH 1.9, Ni 40.1 g./l., Cu 48 mg./l., Fe 62 mg./l. (e) Composition of anode at this time:

Ni 75.8%, Cu 0.65%, Fe 0.6%, S 20.9% The second step (neutralizing electrolysis): The above anode waste liquid is placed in a one-litre beaker and neutralizing electrolysis is effected. (a) Electrolyte (above anode waste liquid) (b) Anode (nickel matte) Ni 75.8%, Cu 0.65%, F; 0.5%, S 20.9%

4 (c) Cathode, Cu and Cu rod (d) El. voltage 5.5 v., el. current 1 A., time 20 minutes,

current density, anode 150 a./m. cathode 5,000 a./m. (2) Finished liquid at this time, ph 4.8, Ni 40.6 g/l.,

Cu 49 rug/1., Fe 78 mg./l.

(f) By-produced nickel powder about 0.2 g.

The third step (liquid refining process): (a) Deferrization: Above finished liquid is shifted to two-litre beaker and stirred in air for 20 minutes, then it is filtrated and Fe of filtrate is found to be lowered to 0.9 mg./l. (that is, only oxidation and no neutralization is required).

(b) Decuprization (copper removing): About 0.3 g. of reducing nickel powder is put in above filtrate and mechanically stirred for 30 minutes at 60 C. and after Cu is replated, it is filtrated and found the Cu to become 0.8 mg./l.

In the present invention, an example for neutralizing electrolysis of the second step is disclosed in detail as follows.

Example 2.-Neutralizing Electrolysis The following table sets forth the results:

Time (minutes) 0 p 1.9 2.23 2.45 29. 92 3.70 4.50 Voltage 10. 6 10. 5 10. 5 10. 6 10. 7 Temp. C.) 43 43 44 44 44.5 45

(2) In case crude nickel anode and copper alloy cathode are used:

Crude nickel anode (Cu 0.95%, Fe 1.32%, Ni 95.7%,

C 1.2%, Si 0.5%)

Cathode (A1 8.5%, Cu rest) Waste liquid of the first step (Ni 45.5 mg./l., Fe 53 mg./l., pH 2.1)

Quantity of liquid, 2,5000 1.

Current density, anode A./m. cathode 5,000 A./m.

El. current, 2,000 A.

The following table sets forth the results:

Time (minutes) 0 10 20 30 M1 2. l. 2. 7 3. 52 4. 57 vnli'mm 7. 8 7. 6 7. 5 7. 5 Temp. C.) 45 45 46 46 (3) In case depolarized anode and copper alloy cathode are used:

Anode (Cu 0.03%, Fe 0.04%, O 0.16%, S 0.005%, Ni

rest) Cathode (A1 9.0%, Cu rest) Waste liquid of the first step (Ni 42.8 mg./l., pH 1.9)

Quantity of liquid, 2,500 1.

Current density, anode A./m. cathode 4,500 A./m.

El. current, 1,900 A.

The following table sets forth the result:

Time (minutes).

The following table sets forth the result:-

Tlme (minutes) 20 pH 1. 9 3.2 4.6 olta 6.0 5.9 5. 9

Temp. C.) 48 49 49 In each of the above examples, almost no nickel is deposited on the cathode plate, but a part of Ni(OH) is precipitated on the tank bottom. Since this Ni(OH) has far better filtrability than the Ni(OI-I) obtainable by precipitating NiSO, with NaOH, it is easily dehydrated by a centrifugal separator and further, because of small contents of Fe, Cu, adsorbed electrolyte is washed by water, then it is dried and roasted into NiO, which is reduced by H gas at 450 C. and reducing nickel powder for removing of copper is made, which is a reducing nickel powder having very good activity. Further, since the anode slime (in case of direct electrolysis of nickel matte in the first step) has its S content of about 95%, it is admixed with sulphur fixing agent comprising lime compounds or natrium compounds and utilized as sulphur supply source for garnierite ore smelting refining, or the slime is dried and sublimation of its sulphur content takes place in a heating furnace without air, then cooled and thus the sulphur of high purity may be recovered.

Thus, it can be seen that the process of this invention is an ingenious combination of steps wherein nickel electrolysis is effected with a nickel matte anode, then a neutralizing electrolytic step is undertaken wherein the neutralization of acid is eifected by generating hydrogen especially with excess cathode current density with the anode being nickel matte or crude nickel, then a liquid refining step is employed.

Various changes and modifications may be made without departing from the spirit and scope of the present invention and it is intended that such obvious changes and modifications be embraced by the annexed claims.

Having thus described the invention, what is claimed as new and desired to be secured by Letters Patent, is:

1. In a process of electrolytically producing nickel, wherein as a first step a nickel matte anode is electrolyzed in an electrolytic bath containing a cathode to deposit nickel at said cathode and to produce an impure highly acid anolyte, the improvement which comprises subjecting said anolyte to an electrolytic neutralization step in an electrolytic system including said anolyte as electrolyte, a nickel-containing anode and a cathode, wherein the surface area of the cathode is maintained substantially smaller than that of said anode while the electrolytic current density at the cathode is maintained substantially greater than at the anode to obtain current conditions wherein the equilibrium potential of nickel is smaller than the equilibrium potential of hydrogen, thereby to dissolve nickel at the anode side while substantially no nickel is deposited at the cathode, to liberate hydrogen at the cathode due to the electrolysis of water and to form nickel hydroxide in said electrolyte to cause the neutralization of said electrolyte, thereafter subjecting said neutralized electrolyte to a third refining step to remove iron and copper impurities, and then recycling the refined neutralized electrolyte to said first step.

2. In a process as claimed in claim 1, wherein the current density at said cathode is maintained at about between 4,500 to 5,000 A./m.

3. In a process as claimed in claim 1, wherein said nickel-containing anode is selected from the group of materials consisting of pure nickel, depolarized nickel and carbonized nickel.

4. In a process as claimed in claim 1, wherein the cathode in said neutralization step is selected from the group of materials consisting of nickel, copper, iron and alloys thereof.

5. In a process as claimed in claim 1, further comprising the step of adjusting the current conditions to obtain a value wherein the equilibrium potential of nickel is substantially equal to that of hydrogen, whereby nickel powder is formed at the cathode side.

6. A process of electrolytically producing nickel, which comprises an electrolytic nickel producing step wherein a nickel matte anode is electrolyzed in an electrolytic bath containing a cathode to deposit nickel at said cathode and to produce an acid waste liquor, an electrolytic neutralization step wherein said waste liquor is subjected to electrolysis in an electrolytic system including said waste liquor as electrolyte, an anode selected from the group of materials consisting of pure nickel, depolarized nickel and carbonized nickel and a cathode selected from the group of materials consisting of nickel, copper, iron and alloys thereof, the surface area of said cathode being substantially larger than that of said anode and the current density at said cathode being maintained substantially greater than at said anode to obtain electrolytic conditions wherein the equilibrium potential of nickel is smaller than the equilibrium potential of hydrogen, whereby nickel is dissolved from the anode while substantially no nickel is deposited at the cathode and hydrogen is liberated at the cathode while nickel hydroxide is formed in the electrolyte, and a refining step for removing iron and copper impurities from said neutralized waste liquor whereafter the refined waste liquor is recycled to said electrolytic nickel producing step.

7. In a process as claimed in claim 6, wherein said nickel producing step produces anode slime, said slime being used as a sulfur source for the production of nickel matte.

8. In a process as claimed in claim 6, wherein said nickel producing step produces anode slime, and refining said slime to obtain pure elementary sulfur and nickel matte.

References Cited in the file of this patent UNITED STATES PATENTS 805,969 Hybinette Nov. 28, 1905 1,003,092 Dow et al. Sept. 12, 1911 1,144,680 Allers June 29, 1915 1,395,827 Hybinette Nov. 1, 1921 1,569,137 Peck et al. Jan. 12, 1926 1,577,422 Hybinette Mar. 16, 1926 2,066,347 Gronningsaeter Jan. 5, 1937 2,115,019 Gronningsaeter Apr. 26, 1938 2,478,189 Gronningsaeter Aug. 9, 1949 

1. IN A PROCESS OF ELECTROLYTICALLY PRODUCING NICKEL, WHEREIN AS A FIRST STEP A NICKEL MATTE ANODE IS ELECTROLYZED IN AN ELECTROLYTIC BATH CONTAINING A CATHODE TO DEPOSIT NICKEL AT SAID CATHODE AND TO PRODUCE AN IMPURE HIGHLY ACID ANOYLYTE, THE IMPROVEMENT WHICH COMPRISES SUBJECTING SAID ANOLYTE TO AN ELECTROLYTIC NEUTRALIZATION STEP IN AN ELECTROLYTIC SYSTEM INCLUDING SAID ANOLYTE AS ELECTROLYTE, A NICKEL-CONTAINING ANODE AND A CATHODE, WHEREIN THE SURFACE AREA OF THE CATHODE IS MAINTAINED SUBSTANTIALLY SMALLER THAN THAT OF SAID ANODE WHILE THE ELECTROLYTIC CURRENT DENSITY AT THE CATHODE IS MAINTAINED SUBSTANTIALLY GREATER THAN AT THE ANODE TO OBTAIN CURRENT CONDITIONS WHEREIN THE EQUILIBRIUM POTENTIAL OF NICKEL IS SMALLER THAN THE EQUILIBRIUM POTENTIAL OF HYDROGEN, THEREBY TO DISSOLVE NICKEL AT THE ANODE SIDE WHILE SUBSTANTIALLY NO NICKEL IS DEPOSITE AT THE CATHODE, TO LIBERATE HYDROGEN AT THE CATHODE DUE TO THE ELECTROLYSIS OF WATER AND TO FORM NICKEL HYDROXIDE IN SAID ELECTROLYTE TO CAUSE THE NEUTRALIZATION OF SAID ELECTROLYTE, THEREAFTER SUBJECTING SAID NEUTRALIZED ELECTROLYTE TO THE THIRD REFINING STEP TO REMOVE IRON AND COPPER IMPURITIES, AND THEN RECYCLING THE REFINED NEUTRALIZED ELECTROLYTE TO SAID FIRST STEP. 